I don't know as I haven't read the story. But typically, in a story titled like this, Iris might be one of the main characters. There could also be other characters related to Iris, such as her friends, family or enemies.
Since I'm not familiar with this story, I can't really give a proper summary. However, if it's a mystery story, perhaps it involves a complex plot with some hidden secrets in the shadow of a character named Iris. But this is just speculation.
In novels, the Prince of Demons usually did not directly PK the Princess because the Princess was usually a character in a novel or anime that represented a specific country or power, while the Prince of Demons was another character that represented a different power or goal.
In some novels or anime, there might be a battle between a demon prince and a princess, but it was usually because of a conflict of interest or goals between the two parties, not because the princess herself had evil characteristics. Therefore, the plot of the Demon Prince vs. Princess might appear in specific novels or anime.
Well, 'light vs shadow light novel' could center around the concept of duality. The light might symbolize good, hope, or positive forces, while the shadow could stand for evil, mystery, or negative aspects. It may tell a story of a hero from the side of light facing challenges from the shadowy elements in the story's universe, with lots of plot twists and character development.
Since I haven't read the novel, I can't say for sure who the main characters are. They could be a hero who embodies light and a villain who represents shadow.
I recommend " The Tsundere School Hunk Lives Next Door." It's similar to the story of the cold-blooded princess and the icy prince. It's also a campus romance theme, and there are many happy fights and bickering scenes. I hope you like my recommendation. Muah!